Yemeni opposition leaders have dismissed the country's president's stance on a revised Gulf-backed plan to ease him out of power, as massive demonstrations keep up pressure on Ali Abullah Saleh to resign.

The rejection on Friday came a day after Saleh refused to sign the deal until representatives of both the ruling party and the opposition sign it, postponing the signing ceremony indefinitely.

Sultan Atwani, an opposition leader, told reporters his bloc would not accept the plan proposed by the Gulf Co-operation Council that envisages Saleh stepping down in 30 days in the hope that would end three months of political crisis.

There were also large anti-government protests in Taiz, Yemen's second city. "Do not leave the places of protest until the fall of the tyrant," a religious leader told crowds.

But Saleh hit back, telling a mass rally of supporters after Friday prayers that he would resist calls to quit, describing as "outlaws" the tens of thousands of protesters gathered a few kilometres away.

"I can assure you that I will resist," Saleh told pro-government crowds in Sabbine Square in Sanaa, the capital.

Ahmed Khalifa al-Kaabi, a media official for Gulf Co-operation Council (GCC), the six Gulf Arab nations sponsoring the agreement, said their foreign ministers would meet in the Saudi capital, Riyadh, on Sunday to try to find a way to salvage a deal.

Al-Kaabi's citing of Saleh's refusal to personally sign the deal indicated the GCC blamed him for the deadlock.

Government officials said Saleh had told GCC secretary-general Abdullatif bin Rashid al-Zayani on Saturday that he intended to ratify the deal after sending a close aide and a senior ruling party official to sign it.

The standoff between Saleh and the hundreds of thousands of street protesters demanding his immediate departure after 32 years in office threatens to pull the impoverished and fragile nation into greater disorder.

The GCC offered a deal that calls for Saleh to step down within 30 days and for the ruling party and the opposition to come together in a national unity government. In exchange, Saleh would get immunity from prosecution.

Yemen's opposition parties, which had initially agreed to the deal, said they would not sign it if Saleh refused to do so personally.

For their part, representatives of those staging anti-government demonstrations since early February have rejected the deal outright, demanding that Saleh immediately step down and face trial for the killings of protesters and corruption.

More bloodshed

They say the established opposition political parties taking part in the talks do not represent them, and even if a deal were reached it seemed unlikely that it would end the protests.

In what appeared to be a last-minute bid to salvage the deal, Saudi Arabia's King Abdullah spoke to Saleh by telephone on Sunday, according to a Yemeni government statement.

The deal's collapse would raise the prospects of more bloodshed in a nation already beset by serious conflict and deep poverty.

At least 140 people have died in the government's crackdown on the protests, which have nonetheless grown in number week after week. The violence has prompted several top military commanders, ruling party members, diplomats and others to defect to the opposition.

Still, Saleh has clung to power and has the key backing of Yemen's best-trained military units, which he placed under the command of one of his sons and other close relatives.